Correlation Analysis of Heavy Metals (Zn, Cd, Cu, Pb) and Fluoride in Groundwater of Nawa Tehsil: Environmental and Health Implications

Abstract

This study investigates the correlation between heavy metals (Fe, Zn, Cd, Cu, Pb) and fluoride in groundwater of Nawa Tehsil, Nagaur District, Rajasthan, focusing on environmental and health implications. Groundwater samples from 12 hand pump locations were analyzed during pre-monsoon (May 2024) and post-monsoon (October 2024) seasons. Fluoride concentrations ranged from 1.3–4.5 mg/L (pre-monsoon) and 1.1–4.0 mg/L (post-monsoon), with 67% of sites exceeding WHO limits (1.5 mg/L), indicating severe geogenic contamination from fluoride-bearing minerals like fluorite and apatite under alkaline conditions (pH 7.5–8.5). Iron levels (0.10–0.45 mg/L pre-monsoon, 0.07–0.34 mg/L post-monsoon) exceeded WHO guidelines (0.3 mg/L) at 50% of sites pre-monsoon, while lead exceedances occurred at 42%. Total dissolved solids (1420–2320 mg/L pre-monsoon, 1210–2050 mg/L post-monsoon) and hardness (212–612 mg/L as CaCO₃ pre-monsoon) indicate poor water quality, unsuitable for direct consumption in most locations except Dalelpura and Govindi. Strong correlations between fluoride and pH (r=0.78), bicarbonate (r=0.72), and TDS (r=0.69) suggest geochemical controls via mineral dissolution and anion exchange. Moderate correlations between fluoride and iron (r=0.58) and zinc (r=0.52) indicate potential synergistic mobilization. Seasonal reductions (12–18% for TDS, 10–15% for fluoride) reflect monsoon dilution, yet contamination persists. These findings highlight significant health risks, including dental/skeletal fluorosis and heavy metal toxicity, necessitating integrated treatment strategies like reverse osmosis or activated alumina to ensure safe drinking water and sustainable agriculture in Nawa Tehsil.